Prolactin deficiency refers to the inability of the pituitary gland in the brain to produce more prolactin hormone than it normally does.

In women, prolactin deficiency is considered to be below approximately 15 to 25 µg/L, and in men, below 5 to 10 µg/L. Prolactin deficiency is caused by damage to the pituitary gland, which secretes the prolactin hormone. Certain health problems and some medications can also cause prolactin deficiency.